llvm/llvm/lib/CodeGen/PostRAHazardRecognizer.cpp

//===----- PostRAHazardRecognizer.cpp - hazard recognizer -----------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
/// This runs the hazard recognizer and emits noops when necessary.  This
/// gives targets a way to run the hazard recognizer without running one of
/// the schedulers.  Example use cases for this pass would be:
///
/// - Targets that need the hazard recognizer to be run at -O0.
/// - Targets that want to guarantee that hazards at the beginning of
///   scheduling regions are handled correctly.  The post-RA scheduler is
///   a top-down scheduler, but when there are multiple scheduling regions
///   in a basic block, it visits the regions in bottom-up order.  This
///   makes it impossible for the scheduler to gauranttee it can correctly
///   handle hazards at the beginning of scheduling regions.
///
/// This pass traverses all the instructions in a program in top-down order.
/// In contrast to the instruction scheduling passes, this pass never resets
/// the hazard recognizer to ensure it can correctly handles noop hazards at
/// the beginning of blocks.
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
usingnamespacellvm;

#define DEBUG_TYPE …

STATISTIC(NumNoops, "Number of noops inserted");

namespace {
  class PostRAHazardRecognizer : public MachineFunctionPass { … };
  char PostRAHazardRecognizer::ID = …;

}

char &llvm::PostRAHazardRecognizerID = …;

INITIALIZE_PASS(…)

bool PostRAHazardRecognizer::runOnMachineFunction(MachineFunction &Fn) { … }